1. Field of the Invention
The present invention is generally concerned with printing machines including at least one object support rotatably mounted on a conveyor which moves forward stepwise, at least one radiation type drying oven disposed in vertical alignment with the path of movement of the object support and drive means for rotating the object support in line with the drying oven while the conveyor is stopped.
It is more particularly directed to the situation in which, for mechanical reasons, it is possible to rotate the object support only when the conveyor carrying it is completely or substantially completely stopped.
When the object support carrying an object which has previously received printing to be dried reaches the drying oven a non-negligible portion of the perimeter of the object is exposed to the corresponding radiation even before the object begins to rotate and likewise as the object support moves away from the drying oven the same part of the perimeter of the object continues to be exposed to the radiation for some time even though the object is no longer rotating.
2. Description of the Prior Art
At present the object support usually rotates at constant speed. The reason for this is that the corresponding drive means are normally coupled to those which drive the printing means and more generally to those which drive the machine as a whole.
The part of the perimeter of the object which is exposed to the radiation before the object begins to rotate and after it begins to rotate therefore receives a much greater quantity of drying energy than the other part of its perimeter, which is prejudicial to the drying process.
U.S. Pat. No. 4,592,276 attempts to avoid this drawback by means of a mechanical arrangement.
This is difficult to implement in practise, however.
The object of the present invention is an arrangement which avoids this drawback in a very simple and reliable manner.
It is based on the idea of making the drive means operative during drying independent of the drive means operative during printing, the drive means including separate digitally controlled motors, for example.